Confinement of Ionic Liquids at Single-Ni-Sites Boost Electroreduction of CO2 in Aqueous Electrolytes

The development of strategies to enhance the electrocatalytic properties of single-atom catalysts is highly desirable, yet challenging. Here we show a versatile nanoconfined ionic liquids (ILs) design to tune the interactions between CO2 and single-Ni-site, meanwhile create a solid/liquid interface with high CO2 concentration for efficient CO2 electrocatalysis. The Ni–N catalyst confined with ILs can be directly used with aqueous electrolytes to mitigate the mass transport and conductivity issues typically associated with viscous bulk ILs electrolytes. Density functional theory studies reveal that the d-band center of Ni atoms is positively shifted to the Fermi level in the presence of IL, and consequently the energy barrier of the rate-limiting step of CO2 reduction, CO2(g) → COOH*, drops significantly from 1.49 to 0.80 eV. The nanoconfined ILs intensify CO2 conversion by showing a high CO Faradaic efficiency of above 98%, enhanced current densities up to 66.1 mA cm–2, and robust stability over 50 h.